1. Field of the Invention
This invention relates to the field of plating and particularly to the field of quality control of plating baths.
2. Description of the Prior Art
Quality control of plating baths is a difficult problem because plating is a complex process involving many ingredients in the plating bath. Small fluctuations in the concentration of ingredients at the electrode surface, especially organic additives, significantly affect brightness, morphology, and mechanical properties of the deposit.
One method used to control the quality of a plating bath is to form a test specimen from plated material and then tensile test the specimen to determine the mechanical properties of the material. The major problem encountered in forming tensile test specimens is to provide uniform, reproducible solution mass transport to the surface being plated. Previously, some combination of conventional stirring, gas bubbling, electrolyte recirculation, or ultrasonic agitation had been relied upon to transport solution species to the electrode. Because agitation thus provided is neither reproducible nor uniform, results of tensile testing the deposited material have not been reliable.
Additional problems are more intimately associated with the sample geometry. Tensile test specimens are generally cut or stamped from larger foils plated on flat stainless steel panels, or are plated directly in the test configuration on masked panels. Since deposits tend to fall off smooth substrates during plating, the steel panels are often roughened to promote sample adhesion. Irregularities in such cut or stamped edges and rough surface defects thus produced can initiate premature failure, yielding unreliable results. Since specimens are generally thin (.ltoreq.0.05 mm), distortion of the sample near the specimen grips can also be significant, so that many samples fail within the grips. Finally, sample alignment is critical for such thin samples.